Classifying Rocks (pg 136)

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Vocabulary

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texture: the way a rock looks and feels
grains: the small pieces of minerals or other rocks a rock is made up of
igneous rock: a rock that's created from the cooling of magma or lava
sedimentary rock: a rock that forms when pieces of other rocks/plants+animals are pushed together
metamorphic rock: a type of rock formed when an earlier rock is changed by natural forces.

Outline

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How Geologists Classify Rocks

• Rocks make up many parts of earth's crust
  • Mountains, hills, valleys, beaches, etc...
• Geologists study/ collect samples of rock to classify them
• There are different ways you classify rocks in the mountains
  • Camera/notebook to record information
• Use chisel to remove samples to study
• Rock samples- geologists study color, texture, and chemical composition

Texture

• Minerals need more than color to classify
  • Texture is another way
• Rocks/grains give texture
  • Geologists use different terms to classify texture
    • Number of terms, like size, shape pattern, etc...

Grain Size

• Some grains are large and easy to see
• Some grains are small and need microscopes
  • Differences in fine-grained, and coarse-grained

Grain Shapes

• Vary in shape
• Some rocks shape in crystals, that form rocks
• Differences in shape

Grain Pattern

• Grains in rock usually form patterns
• Lots of different patterns
  • Contrast, random, etc...

No Visible Grain

• Some have no grain
• When some form, cool quickly
• Some have no crystals
  • Some rocks have visible grain, some don't

Mineral Composition

• Some geologists use tests
  • On rocks, surface, or compounds

Origin

• Three major groups- Igneous, metamorphic, sedimentary
  • Igneous- cooling of molten rock
  • Metamorphic- Rock is changed by heat, pressure, of chemical reaction
  • Sedimentary- Particles joined together

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